ventilation and possible condensation

We moved into a custom victorian house (7yrs old) a few months ago. A couple weeks after moving I noticed some very light tan spots on the ceiling. They didn't look like traditional water stains--they are much lighter and no rings. I also noticed some areas where similar stains had been painted over. None of this was noticed during inspection by our inspector, realtor, my husband, or myself. They cause of these stains is driving me crazy. Now I am thinking it may be improper ventilation.

The area where these stains appeared has a roof seperate from the rest of the house. The house is two story with a wrap-around porch. The wrap-around porch roof continues to the back of the house and covers two rooms of the house. The pitch of this roof is very low (hardly any rise) and there is no attic access to this area. The only ventilation I can see are eave vents. Should there be more? This roof meets up with the rest of the house, so there isn't really a ridge to vent. I know very little about roofing, but I really want to make sure these stains don't come back. Do you think I may be thinking along the right lines?

Is it possible to add ventilation with no attic access without having to rip out my ceiling? (please say yes)

ventilation and possible condensation

Thanks Ed.

I should have been more clear. The stains I can see that were painted over are barely visible and I'm sure were not properly primed. It doesn't seem as though the stains come back in the same spot once they are painted over, and no new spots have appeared in the past three months. I guess I am just anticipating that more will appear and trying to figure out the cause of the old ones.